Abstract:Growth processes of soybean plants under the stress of different Cd2+ concentrations and the changes of chlorophyll contents, SOD (superoxide dismutase) activities, POD (Peroxidase) activities and MDA (malondialdehyde) contents in their leaves during the whole growth cycle were studied through pot experiments. The following results were obtained: (1) During the whole growth cycle of soybean plants, the influences of Cd2+ stress on chlorophyll contents, SOD activities, POD activities, and MDA contents in the leaves were very significant (P＜0.01). (2) Growth of the plants were enhanced under low concentrations and short time of Cd2+ stress, and were restrained under high concentrations and long time of Cd2+ stress. Cd2+ concentration begun to restrain the plant heights was 1.00 mg?kg-1, which was far lower than that (250 mg?kg-1) begun to restrain the biomass of the plants. (3) When Cd2+ concentration reached a certain level, there was a very significant positive correlation between the restraining effects on biomass and height of soybean plants and Cd2+ concentration (P＜0.01), which could be used to indicate soil Cd2+ pollution, especially by using the correlation concerning plant height. The sensitivity of chlorophyll content to Cd2+ stress was higher at seeding stage than those at flowering and podding stages. (4) Increase of POD and SOD activities could reduce, to some extent, the injury effects of soybean plants due to membrane-lipid peroxidation caused by Cd2+ stress. However, when Cd2+ concentration reached 2.50 mg?kg-1, further increasing activities of plant protective enzyme system did not make up enough for the soybean plant injury caused by Cd2+ stress. The POD activities of soybean at seedling stage and flowering-podding stage, or the activities of SOD at flowering-podding stage and mature stage, could indicate well Cd2+ pollution level in soil. MDA contents in soybean plants increased under Cd2+ stress, implying peroxidation of membrane reinforced.